diff --git a/src/wp-includes/block-supports/background.php b/src/wp-includes/block-supports/background.php
index ff50be3206837..814586355f76d 100644
--- a/src/wp-includes/block-supports/background.php
+++ b/src/wp-includes/block-supports/background.php
@@ -62,13 +62,15 @@ function wp_render_background_support( $block_content, $block ) {
 		return $block_content;
 	}
 
-	$background_styles                    = array();
-	$background_styles['backgroundImage'] = isset( $block_attributes['style']['background']['backgroundImage'] ) ? $block_attributes['style']['background']['backgroundImage'] : array();
+	$background_styles                         = array();
+	$background_styles['backgroundImage']      = $block_attributes['style']['background']['backgroundImage'] ?? null;
+	$background_styles['backgroundSize']       = $block_attributes['style']['background']['backgroundSize'] ?? null;
+	$background_styles['backgroundPosition']   = $block_attributes['style']['background']['backgroundPosition'] ?? null;
+	$background_styles['backgroundRepeat']     = $block_attributes['style']['background']['backgroundRepeat'] ?? null;
+	$background_styles['backgroundAttachment'] = $block_attributes['style']['background']['backgroundAttachment'] ?? null;
 
 	if ( ! empty( $background_styles['backgroundImage'] ) ) {
-		$background_styles['backgroundSize']     = isset( $block_attributes['style']['background']['backgroundSize'] ) ? $block_attributes['style']['background']['backgroundSize'] : 'cover';
-		$background_styles['backgroundPosition'] = isset( $block_attributes['style']['background']['backgroundPosition'] ) ? $block_attributes['style']['background']['backgroundPosition'] : null;
-		$background_styles['backgroundRepeat']   = isset( $block_attributes['style']['background']['backgroundRepeat'] ) ? $block_attributes['style']['background']['backgroundRepeat'] : null;
+		$background_styles['backgroundSize'] = $background_styles['backgroundSize'] ?? 'cover';
 
 		// If the background size is set to `contain` and no position is set, set the position to `center`.
 		if ( 'contain' === $background_styles['backgroundSize'] && ! $background_styles['backgroundPosition'] ) {
diff --git a/src/wp-includes/class-wp-theme-json.php b/src/wp-includes/class-wp-theme-json.php
index 63e24340732cf..2e7e055800970 100644
--- a/src/wp-includes/class-wp-theme-json.php
+++ b/src/wp-includes/class-wp-theme-json.php
@@ -237,6 +237,7 @@ class WP_Theme_JSON {
 		'background-position'               => array( 'background', 'backgroundPosition' ),
 		'background-repeat'                 => array( 'background', 'backgroundRepeat' ),
 		'background-size'                   => array( 'background', 'backgroundSize' ),
+        'background-attachment'             => array( 'background', 'backgroundAttachment' ),
 		'border-radius'                     => array( 'border', 'radius' ),
 		'border-top-left-radius'            => array( 'border', 'radius', 'topLeft' ),
 		'border-top-right-radius'           => array( 'border', 'radius', 'topRight' ),
@@ -520,10 +521,11 @@ class WP_Theme_JSON {
 	 */
 	const VALID_STYLES = array(
 		'background' => array(
-			'backgroundImage'    => 'top',
-			'backgroundPosition' => 'top',
-			'backgroundRepeat'   => 'top',
-			'backgroundSize'     => 'top',
+			'backgroundImage'      => 'top',
+			'backgroundPosition'   => 'top',
+			'backgroundRepeat'     => 'top',
+			'backgroundSize'       => 'top',
+			'backgroundAttachment' => 'top',
 		),
 		'border'     => array(
 			'color'  => null,
diff --git a/tests/phpunit/tests/block-supports/wpRenderBackgroundSupport.php b/tests/phpunit/tests/block-supports/wpRenderBackgroundSupport.php
index 3fa7da28908a3..8b9627f840a0d 100644
--- a/tests/phpunit/tests/block-supports/wpRenderBackgroundSupport.php
+++ b/tests/phpunit/tests/block-supports/wpRenderBackgroundSupport.php
@@ -139,20 +139,21 @@ public function data_background_block_support() {
 				'expected_wrapper'    => '<div class="has-background" style="background-image:url(&#039;https://example.com/image.jpg&#039;);background-size:cover;">Content</div>',
 				'wrapper'             => '<div>Content</div>',
 			),
-			'background image style with contain, position, and repeat is applied' => array(
+			'background image style with contain, position, attachment, and repeat is applied' => array(
 				'theme_name'          => 'block-theme-child-with-fluid-typography',
 				'block_name'          => 'test/background-rules-are-output',
 				'background_settings' => array(
 					'backgroundImage' => true,
 				),
 				'background_style'    => array(
-					'backgroundImage'  => array(
+					'backgroundImage'      => array(
 						'url' => 'https://example.com/image.jpg',
 					),
-					'backgroundRepeat' => 'no-repeat',
-					'backgroundSize'   => 'contain',
+					'backgroundRepeat'     => 'no-repeat',
+					'backgroundSize'       => 'contain',
+					'backgroundAttachment' => 'fixed',
 				),
-				'expected_wrapper'    => '<div class="has-background" style="background-image:url(&#039;https://example.com/image.jpg&#039;);background-position:center;background-repeat:no-repeat;background-size:contain;">Content</div>',
+				'expected_wrapper'    => '<div class="has-background" style="background-image:url(&#039;https://example.com/image.jpg&#039;);background-position:center;background-repeat:no-repeat;background-size:contain;background-attachment:fixed;">Content</div>',
 				'wrapper'             => '<div>Content</div>',
 			),
 			'background image style is appended if a style attribute already exists' => array(
diff --git a/tests/phpunit/tests/theme/wpThemeJson.php b/tests/phpunit/tests/theme/wpThemeJson.php
index bea22948a500f..fb9d974b1ca29 100644
--- a/tests/phpunit/tests/theme/wpThemeJson.php
+++ b/tests/phpunit/tests/theme/wpThemeJson.php
@@ -4997,12 +4997,13 @@ public function test_get_top_level_background_image_styles() {
 				'version' => WP_Theme_JSON::LATEST_SCHEMA,
 				'styles'  => array(
 					'background' => array(
-						'backgroundImage'    => array(
+						'backgroundImage'      => array(
 							'url' => 'http://example.org/image.png',
 						),
-						'backgroundSize'     => 'contain',
-						'backgroundRepeat'   => 'no-repeat',
-						'backgroundPosition' => 'center center',
+						'backgroundSize'       => 'contain',
+						'backgroundRepeat'     => 'no-repeat',
+						'backgroundPosition'   => 'center center',
+						'backgroundAttachment' => 'fixed',
 					),
 				),
 			)
@@ -5013,7 +5014,7 @@ public function test_get_top_level_background_image_styles() {
 			'selector' => 'body',
 		);
 
-		$expected_styles = "html{min-height: calc(100% - var(--wp-admin--admin-bar--height, 0px));}:root :where(body){background-image: url('http://example.org/image.png');background-position: center center;background-repeat: no-repeat;background-size: contain;}";
+		$expected_styles = "html{min-height: calc(100% - var(--wp-admin--admin-bar--height, 0px));}:root :where(body){background-image: url('http://example.org/image.png');background-position: center center;background-repeat: no-repeat;background-size: contain;background-attachment: fixed;}";
 		$this->assertSame( $expected_styles, $theme_json->get_styles_for_block( $body_node ), 'Styles returned from "::get_stylesheet()" with top-level background styles type does not match expectations' );
 
 		$theme_json = new WP_Theme_JSON(